Study on the Quenching Mechanism of Radicals by Fullerenes (C ₆₀ and C ₇₀ )

Although fullerenes are well-recognized for their exceptional radical-quenching abilities, the molecular-level mechanisms governing their interactions with free radicals remain unclear. Herein, the interactions between C₆₀/C₇₀ and 16 representative radicals were systematically investigated using density functional theory (DFT). The calculated binding energies (-10.21 to -51.26 kcal·mol⁻¹) indicate strong and thermodynamically favorable radical-fullerene associations. Frontier orbital and spin-density analyses reveal that fullerenes act as electron acceptors, facilitating electron transfer from radicals and stabilizing their electronic states. Ab initio molecular dynamics (AIMD) simulations of five typical radicals (•OH, •OOH, CH₃OO•, Ph₃C•, and DPPH) further uncover time-resolved quenching behavior, where spin populations at radical sites rapidly decrease to nearly zero, confirming single-electron transfer as the dominant quenching pathway. Mayer bond-order analysis shows the transient formation of weak covalent bonds enabling reversible radical capture. Complementary electron paramagnetic resonance (EPR) spin-trapping experiments validate these theoretical findings, demonstrating that C₆₀ effectively quenches hydroxyl radicals generated from H₂O₂ photolysis. Moreover, transition-state calculations reveal that C₆₀ catalytically promotes H₂O₂ decomposition by reducing the reaction barrier while maintaining structural integrity. These combined results establish a dual-function mechanism of electron-transfer-driven radical quenching and catalytic ROS decomposition, providing a theoretical foundation for designing fullerene-based antioxidant materials.